Development of a ceramic-ceramic weld by plasma spray

Aluminosilicate powders are used in plasma spray mainly as coatings of no more than a few millimeters. These coatings have high dielectric strength, high hardness, good wear resistance, excellent refractory properties, they are chemically stable, and chemically inert. However in the case of the ceramic-ceramic welding, aluminosilicate powders are very hard to spray in coatings of tens of millimeters due to the high thermal shock that can cause damage at a microscopic and macroscopic scale. In this study the aim is to weld dense ceramic parts through means of plasma spray, by controlling the procedures of heating, spraying, and cooling. Also due to the fact that the ceramic weld will be much more porous than the support, several compositions with different rapports of alumina and silica are tested in order to reduce the difference of thermal expansion coefficients. For the heating and the cooling procedure, a numerical model is established in order to determine the stress at break for the ceramic to be welded. Mechanical tests are performed both on the weld as well as on the ceramic support in order to determine the compatibility between the two materials.